header-files

I was just wondering what the difference between .cpp and .h files is? What would I use a header file (.h) for and what would I use a cpp file for? In general, and it really could be a lot less general: .h (header) files are for declarations of things that are used many times, and are #include d in other files .cpp (implementation) files are for everything else, and are almost never #include d Technically, there is no difference. C++ allows you to put your code in any file, with any format, and it should work. By convention, you put your declarations (basically, that which makes up your API)

I always placed my #include after the #ifdef / #define Include-Guard. Now the refactor mechanism of my IDE (Qt Creator) put it before the Include-Guard e.g. #include "AnotherHeader.h" #ifndef MYHEADER_H #define MYHEADER_H Can this cause any problems or can I leave it this way? If the header in question has include guards itself, you won't run into problems. Putting it inside the include guards may still speed up compilation. Something the compiler does not see takes less time to compile, even if it does not produce any errors. Although less common, I believe this is considered to be acceptable

This header file shall define NULL or size_t and other macros, but I find that /usr/include/linux/stddef.h is empty? Why? The actual location of the headers is implementation defined. What you look at is not the typical <stddef.h> included by gcc. You can find out exactly where it's located on your system with: gcc -E - <<<'#include<stddef.h>' | grep stddef.h which is equivalent to including the header <stddef.h> in an empty C file and running gcc -E on it. The headers in /usr/include/linux are used to compile the C library (usually glibc on Linux). The GNU manual says: The linux , asm and asm

On the question C/C++ include file order/best practices , the best answer recommends to include the related header first. Same for Google and Mozilla style guides. However, in both cases, I couldn't find a good reason why you would do this. Google and Mozilla coding rules look best to me, because they enforce you to include the most "standard" headers first. This way, I think you are less likely to mess up the included files (for examples by undefining some macros used in the other headers etc.) so that looks like the best way to go for me. But following that rationale, why would you include

This question already has an answer here: What should go into an .h file? 12 answers I'm trying to create a simple program that takes input from the user in C++ using good programming practices. It consists of Input.hpp, Input.cpp and main.cpp. I keep getting a multiple definition error even though I am using ifndef to prevent that. Input.hpp #ifndef Input_HPP #define Input_HPP #include <string> #include <vector> using namespace std; vector<string> Get_Input(); vector<string> input_array; string starting_position; int input_number; #endif Input.cpp #include <iostream> #include <cmath> #include

During compilation I get a "multiple definition" error, which refers to a template specialisation in a header file. Do I need to put the specialisations into the source file? If it is functions you have specialized, you can either put them in the .cpp file, or make them inline in the header. Like James points out, if you don't make the functions inline, you still have to declare the specializations in the header. Otherwise the compiler doesn't know it has to look for them elsewhere. You can then put the implementations (definitions) in a .cpp file. Just like with other functions. No, you don't

Can somebody please explain this? #include <iostream> #include <limits.h> or #include <iostream> #include <limits> <limits> is a C++ Standard Library header providing similar insights to the C header <limits.h> (which is also available in C++ as <climits> ), but it is written in a way that's more useful and safe in C++ programs: say you have a template <typename Numeric> ... , and the code inside wants to know the minimum and maximum value of the Numeric type parameter that the user instantiated your template with: you can use std::numeric_limits<Numeric>::min() and ...::max() ; if you wanted